1. Field of the Invention
The invention relates to a circuit arrangement for transmitting information between at least a subscriber terminal and an exchange over a transmission line connected to the terminal and the exchange by means of adapting circuits, the adapting circuits each comprising two sub-circuits interconnected via a modular first interface and of which the first sub-circuit which is located nearest to the transmission line is essentially the same for the two adapting circuits and comprises the physical adaptation to the transmitting medium.
2. Related Art
Such a circuit arrangement for a so-called ISDN communications network is, for example, known from the brochure of SIEMENS "ICs for Telecommunications, IOM, ISDN Oriented Modular Interface, Interface Description". In the above brochure specifically the first interface between the two sub-circuits is described. The first sub-circuit is then especially arranged for a copper cable as a transmitting medium and transmits through this cable the digital information as ternary signals and comprises the converting circuits and line amplifiers required for that purpose. This sub-circuit further includes processing and converting arrangements for processing the control signals transmitted over the first interface and converting the data also transmitted over this interface into the ternary line signals and vice versa, so that the first sub-circuit has a complex structure. When employing a glass fibre link as a transmitting medium, a novel sub-circuit of a similarly complicated structure has to be developed.